Evaluation of optoelectronic response and Raman active modes in Tb3+ and Eu3+-doped gadolinium oxide (Gd2O3) nanoparticle systems

Abstract

Rare earth oxide (Tb3+ :Gd2O3 and Eu3+ :Gd2O3) nanophosphors are exploited through spectroscopic and microscopic tools with special emphasis on D–F mediated radiative emission and Raman active vibrational modes. Powder X-ray diffraction measurements have revealed cubic crystal structure of the nanosystems and with an average crystallite size varying between ~3.2 and 4.8 nm. Photoluminescence (PL) spectra of Tb3+ doped systems signify intense blue-green (~490 nm) and green (~544 nm) emissions mediated by 5 D 4 → 7 F 6 and 5 D 4 → 7 F 5 transitional events; respectively. In the PL responses of Eu3+ doped nanoparticle systems, we also identify magnetically-driven 5 D 0 → 7 F 1 (~591 nm) and electrically driven 5 D 0 → 7 F 2 (~619 nm) radiative features which seem to improve with increasing doping level. However, the magnitude of Judd–Ofelt (J–O) intensity parameters (Ω 2, 4), is significantly lowered for the high doping cases. Raman spectra of the undoped and RE doped systems exhibited several Ag and Fg modes in the range of Raman shift ~100–600 cm−1. In the Raman spectra, the peaks located at ~355 cm−1 are assigned to the mixed mode of F g + A g, the line width of which was found to increase with RE doping. Moreover, owing to the enhanced defect concentration in the doped systems than its undoped counterpart, we anticipate a faster phonon relaxation and consequently, a suppression of phonon lifetime in the former case.